Just wanted to chime in my thoughts on this. I have tried numerous diaper bags and have only liked the backpacks. There's a couple of reasons for this. When I have a shoulder bag on and bend over to attend to a child, it always swings forward and hits them! I've found that very annoying. Also, when the diaper bag is on my back, it's out of the way. I have 2 free hands for holding hands, I can unfold my stroller or fold it up, really just about anything. When I need to get something out of it, I just swing it off one shoulder and reach around. It's really not a problem for me. In fact, I 've been able to wear it on my back while slinging an infant in front.
I have had the Petunia Picklebottom Boxy backpack and LOVED. It is roomy, comfortable, has plenty of pockets and the patterns are darling. However, the fabric is delicate and is only dry cleanable. So, I tried the Jujube Packabe which when I was looking was the largest Jujube backpack they created and honestly, it is a workhorse. I have that thing filled to the top all the time and it is heavy. But it is still in fantastic shape after nearly 2 years with twins and a toddler's stuff to carry around. It can be worn as a backpack or a shoulder bag. The zippers are sturdy and it has a lot of organization. The magnet closures on the front pockets are VERY strong too. The outside fabric is wipeable-yay! I honestly have no complaints about it.
Until recently, I carried 2 sizes of diapers, wipes, a single change of clothes for the twins, a change of clothes that could fit either of my older boys, bottles, juice boxes and a little snack for the boys, my wallet, a little makeup bag for me, my cell phone and some miscellaneous things like little toys and crayons for the boys. It all fit in there.
hth and good luck with your pregnancy!
" I object to violence because when it appears to do good, the good is only temporary; the evil it does is permanent." Mahatma Gandhi
"This is the ultimate weakness of violence: It multiplies evil and violence in the universe. It doesn't solve any problems." Martin Luther King, Jr.